Black triangles in mesh
Often times faces appear darker if their normals are flipped. In computer games these faces are usually not rendered. Blender however makes sure that they are and hints to the user that the normals are flipped. To test if it's a normal issue you should check enable backface culling in the 3D views properties panel 



Your faces however seem pitch black thus this could imply a few things:


Faces are assigned to a material which is pitch black
Faces are mapped to a black/empty region in your texture
You're seeing the vertex colors assigned to the vertices.


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